This invention relates to an engine operational control unit and more particularly to a method and apparatus for controlling an engine under abnormal conditions.
A common form of throttle control for an internal combustion engine has a remotely positioned throttle control operated by the operator. This throttle control is connected by means of an interconnecting mechanism such as a howden wire actuator or the like to the actual throttle of the engine for controlling the engine speed. However, in some instances, due to various forms of malfunction, the actual position of the throttle of the engine may not coincide in position with the operator throttle control. When this occurs, there is obviously a serious problem that requires protective action.
For example, in many types of vehicles, the throttle control and interconnecting mechanism is exposed to severe atmospheric conditions that can adversely affect the operation. For example, in snowmobiles the throttle linkage or bowden wire mechanism can easily become encrusted with ice or snow, and the throttle of the engine may become stuck in a position that can cause problems.
It has been proposed to provide a comparator that senses the position of the throttle control and the throttle and which will shut off the engine by discontinuing the supply of current to the spark plugs for their firing when this condition occurs. Although this system has advantages, it can present certain difficulties.
For example, if the ignition is shut off while the engine is running, the engine will obviously not stop immediately. As a result, the engine will operate as a pump and will draw fuel into the engine and discharge it to the atmosphere until the engine stops turning. This can give rise to problems not only with emission, but also can give difficulties on restarting.
For example, if fuel continues to be pumped through the engine when the ignition is shut off, the spark plugs will become wetted and foul, and restarting with the same spark plugs can very well become impossible.
A solution to this problem would be to also discontinue the supply of fuel to the engine when the ignition is shut off. However, this can be detrimental to the engine. For example, if the engine has been running at-a high speed, and a discrepancy occurs between the position of the throttle control and the position of the throttle, and the ignition and the fuel supply are shut off, then the engine will be deprived of any fuel while it continues to turn. This will mean that there is no cooling of the engine due to the vaporization of the fuel, and damage to the engine can result.
It is, therefore, an object of this invention to provide an improved engine control method and apparatus for protecting an engine in the event of abnormal conditions.
It is a further object of this invention to provide an improved engine control apparatus and method for protecting an engine by discontinuing its operation under abnormal conditions, but at the same time ensuring that damage to the engine will not occur and restarting is facilitated.
Another difficulty with the stopping of an engine under the abnormal condition of throttle position and throttle control position is that restarting of the engine can be difficult, as aforenoted. In addition to the wetting of the spark plugs and possible fouling, the ambient conditions may be such that it would be difficult or impossible to start the engine after the defect has been remedied.
It is, therefore, a still further object of this invention to provide an engine control apparatus and method for protecting an engine in the event of an abnormal condition by discontinuing its operation but then re-energizing the engine once the speed has fallen to a safe speed and maintaining the running at that new, safe, lower speed.